INSPECTION AND MONITORING OF REINFORCED-CONCRETE STRUCTURES - ELECTROCHEMICAL METHODS TO DETECT CORROSION

Maintenance and planning of the restoration work on reinforced concret e structures need a rapid, non-destructive inspection technique that d etects corrosion at an early stage. In this paper the field experience with electrochemical techniques are reported. The results of potentia l surveys on bridge decks and walls realised with a new computer-contr olled eight-wheel measurement system clearly show that a fixed potenti al value (as proposed in ASTM C 876-87) for the identification and loc ation of active corrosion of steel in concrete does not exist. A stati stical elaboration of the potential data allows to identify the potent ial value for corroding and passive rebars for each structure individu ally. A rapid new technique using galvanostatic pulse measurements was tested successfully on site. It gives clear, unambiguous results on t he corrosion state of the rebars when half-cell potentials are uncerta in. In addition, the ohmic resistance and the apparent polarisation re sistance are determined from the evaluation of the transients. From th ese values, the concrete resistivity and the actual corrosion rate of the rebars may be estimated.